1. Field of the Invention
The present invention relates to an electronic apparatus which is movable easily and quickly, and, more particularly, to a mobile-type electronic apparatus arranged to receive image signals and to display images, and to a control method for controlling the mobile-type electronic apparatus.
2. Description of Related Art
As a result of the recent increase in communication speed, a video conference system is being developed for practical applications. Meanwhile, a mobile-type electronic apparatus, such as a notebook-type personal computer, is being arranged to use a video camera as an accessory thereof.
It is important for such a mobile-type electronic apparatus to arrange a small display to be viewable at a large angle of view with a high picture quality. One of proposals for attaining this purpose has been disclosed in Japanese Laid-Open Patent Application No. Hei 10-191288.
The art disclosed in Japanese Laid-Open Patent Application No. Hei 10-191288 is the arrangement for displaying a virtual image by enlarging a small liquid crystal panel to a predetermined angle of view. In viewing a picture plane of VGA (640×480 dots) on a direct-viewing-type liquid crystal panel, for example, since the resolution of the eye of man is one minute of angle, in order to enable a viewer who is a little presbyopic to see at a distance of 30 cm, the liquid crystal panel must be of a size diagonally measuring “2× 5/4×30×tan( 1/60×640)” cm, i.e., 14.1 cm, with the aspect ratio of the picture plane assumed to be 4:3. According to the art disclosed in Japanese Laid-Open Patent Application No. Hei 10-191288, on the other hand, an image of high picture quality can be displayed by means of a compact display by enlarging a small liquid crystal panel diagonally measuring 0.5 inch (1.27 cm) to a horizontal angle of view of 21.3 degrees.
Mobile-type electronic apparatuses, such as notebook-type personal computers, are arranged in general to use a rechargeable battery as a power source. However, in order to enhance the portability of the apparatus, the body of the apparatus must be reduced in weight and, therefore, must be arranged to save electric energy for use of a battery of small capacity over a long period of time.
An electronic apparatus disclosed, for example, in Japanese Laid-Open Patent Application No. Hei 9-322137 is arranged for this purpose. The electronic apparatus disclosed in Japanese Laid-Open Patent Application No. Hei 9-322137 is arranged to suppress electric energy consumption by cutting off a power supply for an image pickup system including a CCD of a TV (video) camera when the electronic apparatus is not used.
However, in a mobile-type electronic apparatus as mentioned above, an image display function is important as well as an image signal transmitting function. In view of these functions, it is desired to have the apparatus arranged to be small in size, to be light in weight, to be movable easily and quickly and to be usable over a long period time with the battery charged once.
The electronic apparatus disclosed in Japanese Laid-Open Patent Application No. Hei 10-191288 is capable of displaying a high quality image at a large angle of view and also lessening electric energy consumption for illuminating the liquid crystal panel, as compared with a direct-viewing-type liquid crystal panel of a relatively large size. The electronic apparatus, however, has a problem in the following point. If the liquid crystal display panel is arranged to use many pixels such as 180 thousand or 270 thousand pixels or pixels of SVGA for obtaining a high picture quality, a number of times of arithmetic operation to be performed by a control circuit according to image signals coming from such many pixels increases. As a result, electric energy consumption also increases.
The electronic apparatus disclosed in Japanese Laid-Open Patent Application No. Hei 9-322137 is arranged to save electric energy on the side of the TV (video) camera to be used in photo-taking. However, the electronic apparatus is not arranged to suppress electric energy consumption for display. The electronic apparatus thus has a problem in respect of the electric energy consumption on the side of display.
In the case of a mobile-type electronic apparatus, such as a notebook-type personal computer, the use of the electronic apparatus for photo-taking (picking up images) is a special function, as compared with the use of the electronic apparatus for ordinary information display and data processing. The length of time of use of the electronic apparatus for the photo-taking function is expected to be shorter than the use of the electronic apparatus for other functions. The electronic apparatus thus has a problem with respect to the arrangement for increasing its serviceable time obtainable by charging the battery once.